Selective polyamine-binding proteins spermine binding by an androgen-sensitive phosphoprotein

Abstract

Rat ventral prostate contains an acidic protein which can bind spermine selectively. The relative binding affinities of various aliphatic amines for the protein are, in decreasing order, spermine > thermine >> spermidine > putrecine > 1,10-diaminodecane, cadaverine and 1,12-diaminododecane. The binding protein has an isoelectric point at pH 4.3 and a sedimentation coefficient of 3 S. Its molecular weight is approx. 30 000. Histones and nuclear chromatin preparations of the prostate can interact with the binding protein. The spermine-binding activity of the purified prostate protein can be inactivated by treatment with intestinal alkaline phosphatases. The phosphatase-treated preparation can then be reactivated by beef heart protein kinase in the presence of cyclic AMP and ATP. The spermine-binding activity of the prostate cytosol protein fraction decreases after castraction, but increases very rapidly after the castrated rats are injected with 5α-dihydrotesterone. This finding raises the possibility that, in the prostate, certain androgen actions may be dependent on the androgen-induced increase in the acidic protein binding of polyamines and their translocation to a functional cellular site such as nuclear chromatin. In the prostate cytosol, spermine also binds to 4-S tRNAs and to a unique RNA which has a sedimentation coefficient of 1.5 S.